Deterioration or dislocation of a spinal disc located between two adjacent vertebral bodies often results in the two adjacent vertebral bodies coming closer together. The reduced disc space height typically results in instability of the spine, decreased mobility and pain and discomfort for the patient. A common treatment is to surgically restore the proper disc space height to thereby alleviate the neurologic impact of the collapsed disc space. Typically, most surgical corrections of a disc space include at least a partial discectomy which is followed by restoration of normal disc space height and, in some instances, fusion of the adjacent vertebral bodies. Restoration of normal disc space height generally involves the implantation of a spacer and fusion typically involves inclusion of bone graft or bone graft substitute material into the intervertebral disc space to create bony fusion. Fusion rods may also be employed. Some implants further provide artificial dynamics to the spine. Such techniques for achieving interbody fusion or for providing artificial disc functions are well-known in the art.
One problem, among others, with inserting an implant, for example, is associated with patient anatomy. Inserting and positioning the implant in the space between adjacent vertebrae can be difficult or time consuming if the bony portions are spaced too close together, or if the adjacent tissue, nerves or vasculature impedes access to or placement of the implant in the space between the bony portions. Furthermore, maintenance of distraction of the space during insertion of the implant requires additional instruments in the operative space which can make the procedure more invasive and impede access and visibility during implant insertion and thereby make the procedure more difficult.
Another difficulty of implant insertion is related to the point of access to the damaged disc space which may be accomplished from several approaches to the spine with each approach having different associated difficulties. One approach is to gain access to the anterior portion of the spine through a patient's abdomen. For an anterior approach, extensive vessel retraction is often required and many vertebral levels are not readily accessible from this approach. Another approach is a posterior approach. This approach typically requires that both sides of the disc space on either side of the spinal cord be surgically exposed, which may require a substantial incision or multiple access locations, as well as extensive retraction of the spinal cord. Yet another approach is a postero-lateral approach to the disc space. The posterior-lateral approach is employed in a posterior lumbar interbody fusion (PLIF) or transforaminal lumber interbody fusion (TLIF) procedure which may be performed as an open technique which requires making a larger incision along the middle of the back. Through this incision, the surgeon then cuts away, or retracts, spinal muscles and tissue to access the vertebrae and disc space. The TLIF procedure may also be performed as a minimally invasive or as an extreme lateral interbody fusion (XLIF) procedure that involves a retroperitoneal transpoas approach to the lumbar spine as an alternative to “open” fusion surgery. In the minimally invasive procedure, the surgeon employs much smaller incisions, avoids disrupting major muscles and tissues in the back and reduces the amount of muscle and tissue that is cut or retracted. As a result, blood loss is dramatically reduced and these minimally invasive benefits also lead to shorter hospital stays and quicker patient recovery times. The aforementioned and various other difficulties associated with the point of access to the damaged disc space and the need to navigate an implant insertion instrument through the point of access further place demands on the implant insertion instrument design.
Therefore, there remains a need for improved insertion instruments, implants and techniques for use in any one or more types of approaches to the disc space that facilitate and provide for effective insertion while saving time, minimizing the degree of invasiveness for the patient and complementing surgeon skill demands.